ul { margin:5px 0 0 0; padding:0; list-style:none; width:300px; background:#f1f1f1; }
li { border-left:1px solid #fff; border-bottom:1px solid #999; border-top:1px solid #fff; border-right:1px solid #ccc; line-height:28px; text-indent:20px; font-family:arial; cursor:pointer; border-radius:4px; margin-bottom:3px; color:#6f6f7a; transition:0.3s; }
li:hover { border-right:1px solid #fff; border-top:1px solid #999; border-bottom:1px solid #fff; border-left:1px solid #999; background:#6e697a; color:#fff; }
原文：http://www.cnblogs.com/q460021417/p/4299163.html